Representation of fire, land-use change and vegetation dynamics in the Joint UK Land Environment Simulator vn4.9 (JULES)

“…There is a small overestimation of tree fraction in savanna biomes, most notably on the southern edge of the Amazon forest. This is due to the lack of fire disturbance, the inclusion of which would be expected to improve vegetation structure in these regions (Burton et al, 2019). Figure 17 shows the evolution of terrestrial carbon fluxes in the ensemble mean of the historical simulations.…”

Section: Terrestrial Biogeochemistrymentioning

confidence: 99%

UKESM1: Description and Evaluation of the U.K. Earth System Model

Sellar

Jones

Mulcahy

et al. 2019

J Adv Model Earth Syst

Self Cite

503

449

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We document the development of the first version of the U.K. Earth System Model UKESM1.The model represents a major advance on its predecessor HadGEM2-ES, with enhancements to all component models and new feedback mechanisms. These include a new core physical model with a well-resolved stratosphere; terrestrial biogeochemistry with coupled carbon and nitrogen cycles and enhanced land management; tropospheric-stratospheric chemistry allowing the holistic simulation of radiative forcing from ozone, methane, and nitrous oxide; two-moment, five-species, modal aerosol; and ocean biogeochemistry with two-way coupling to the carbon cycle and atmospheric aerosols. The complexity of coupling between the ocean, land, and atmosphere physical climate and biogeochemical cycles in UKESM1 is unprecedented for an Earth system model. We describe in detail the process by which the coupled model was developed and tuned to achieve acceptable performance in key physical and Earth system quantities and discuss the challenges involved in mitigating biases in a model with complex connections between its components. Overall, the model performs well, with a stable pre-industrial state and good agreement with observations in the latter period of its historical simulations. However, global mean surface temperature exhibits stronger-than-observed cooling from 1950 to 1970, followed by rapid warming from 1980 to 2014. Metrics from idealized simulations show a high climate sensitivity relative to previous generations of models: Equilibrium climate sensitivity is 5.4 K, transient climate response ranges from 2.68 to 2.85 K, and transient climate response to cumulative emissions is 2.49 to 2.66 K TtC −1 . Plain Language SummaryWe describe the development and behavior of UKESM1, a novel climate model that includes improved representations of processes in the atmosphere, ocean, and on land. These processes are inter-related: For example, dust is produced on the land and blown up into the atmosphere where it affects the amount of sunlight falling on Earth. Dust can also be dissolved in the ocean, where it affects marine life. This in turn changes both the amount of carbon dioxide absorbed by the ocean and the material emitted from the surface into the atmosphere, which has an affect on the formation of clouds. UKESM1 includes many processes and interactions such as these, giving it a high level of complexity. Ensuring realistic process behavior is a major challenge in the development of our model, and we have carefully tested this. UKESM1 performs well, correctly exhibiting stable results from a continuous pre-industrial simulation (used to provide a reference for future experiments) and showing good agreement

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“…The differences in the defined average burnt areas for these biomes -smaller for trees than grasses -causes an underestimation of fire size in these regions. This overestimation of the tree fraction is attributed to the lack of fire 290 disturbance in the fully coupled UKESM1 configuration, the inclusion of which could potentially improve vegetation structure in these regions (Burton et al, 2019).…”

Section: Resultsmentioning

confidence: 99%

Coupling interactive fire with atmospheric composition and climate in the UK Earth System Model

Teixeira¹,

Folberth²,

O’Connor³

et al. 2020

Preprint

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Abstract. Fire constitutes a key process in the Earth system (ES) being driven by climate as well as affecting the climate by changing atmospheric composition and impacting the terrestrial carbon cycle. However, studies on the effects of fires on atmospheric composition, radiative forcing and climate have been limited to date, as the current generation of ES models (ESMs) do not include fully coupled fires. The aim of this work is the development and evaluation of a fully coupled fire-composition-climate ES model. For this, the INteractive Fires and Emissions algoRithm for Natural envirOnments (INFERNO) fire model is coupled to the atmosphere-only configuration of the UK’s Earth System Model (UKESM1). This fire-atmosphere interaction through atmospheric chemistry and aerosols allows for fire emissions to influence radiation, clouds, and generally weather, which can consequently influence the meteorological drivers of fire. Additionally, INFERNO is updated based on recent developments in the literature to improve the representation of human/economic factors in the anthropogenic ignition and suppression of fire. This work presents an assessment of the effects of interactive fire coupling on atmospheric composition and climate compared to the standard UKESM1 configuration that uses prescribed fire emissions. Results show a similar performance when using the fire-atmosphere coupling (the online version of the model) when compared to the offline UKESM1 that uses prescribed fire. The model can reproduce observed present day global fire emissions of carbon monoxide (CO) and aerosols, despite underestimating the global average burnt area. However, at a regional scale there is an overestimation of fire emissions over Africa due to the misrepresentation of the underlying vegetation types and an underestimation over Equatorial Asia due to a lack of representation of peat fires. Despite this, comparing model results with observations of CO column mixing ratio and aerosol optical depth show that the fire-atmosphere coupled configuration has a similar performance when compared to UKESM1. In fact, including the interactive biomass burning emissions improves the interannual CO atmospheric column variability and consequently its seasonality over the main biomass burning regions – Africa and South America. Similarly, for aerosols, the AOD results broadly agree with MODIS and AERONET observations.

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Representation of fire, land-use change and vegetation dynamics in the Joint UK Land Environment Simulator vn4.9 (JULES)

Cited by 63 publications

References 63 publications

Global ecosystems and fire: Multi‐model assessment of fire‐induced tree‐cover and carbon storage reduction

Global ecosystems and fire: Multi‐model assessment of fire‐induced tree‐cover and carbon storage reduction

UKESM1: Description and Evaluation of the U.K. Earth System Model

Coupling interactive fire with atmospheric composition and climate in the UK Earth System Model

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